1. Field of the Invention
Example embodiments of the present invention relate generally to a semiconductor device and methods thereof, and more particularly to a semiconductor device and methods of protecting a semiconductor device.
2. Description of the Related Art
Electrostatic discharge (ESD) may be generated when a semiconductor device comes into contact with and/or is placed adjacent to an article charged with an electrostatic potential different from the electrostatic potential of the semiconductor device. EDS may be characterized by a greater amount of charges being delivered to the semiconductor device within a shorter period of time period (e.g., less than 1 micro-second (μs)), such that an instant voltage and/or current “spike” may be generated inside the semiconductor device. The instant voltage and/or current spike may exceed an operation threshold of the semiconductor device, may damage a gate insulator of the semiconductor device and may accelerate an electro-thermal failure, such as a contact spike, a melting of silicon, a breaking of wiring, etc. Accordingly, conventional semiconductor devices may include ESD protection circuits in an attempt to reduce the harmful effects of ESD. For example, an ESD protection circuit may be employed at an input terminal of a semiconductor device to protect against ESDs received from an external source.
During a semiconductor fabrication process, charges generated by plasma (e.g., used for gate etching, metal interconnection line etching, photoresist stripping, etc.) may accumulate (e.g., on a gate pattern, a metal interconnection line pattern, etc.).
FIG. 1 is a schematic sectional view illustrating a conventional semiconductor device 100 including a diode for protecting against an ESD.
Referring to FIG. 1, when electrons associated with plasma used in a plasma etching process for forming a metal interconnection line accumulate on a gate conductive layer 17 through a via 32 formed in a metal interconnection line 50 and an insulation layer 60, an ESD may be generated. The generated ESD may damage a gate insulating layer 15. The semiconductor device 100 may be protected against such damage by allowing the current generated due to the ESD to flow through an ESD protection circuit.
Referring to FIG. 1, an N-type impurity region 12 may be formed in a P-type semiconductor substrate 10 to form an NP junction diode. FIG. 2 illustrates a circuit diagram of the NP junction diode of FIG. 1. In an example, the NP junction diode of FIGS. 1 and 2 may function as an ESD protection circuit.
Referring to FIGS. 1 and 2, the metal interconnection line 50 may be connected to the N-type impurity region 12 through a conductive plug 34. If the current generated by the ESD flows through the NP junction diode including the N-type impurity region 12 from the metal interconnection line 50, the semiconductor device 100 may be protected or isolated from the ESD.
Referring to FIG. 1, the ESD may be generated during a packing process after the fabrication process of the semiconductor device 100 is completed. A polyimide layer of a fuse region may be opened in order to cut a fuse connected to a failed cell by irradiating a laser beam and the failed cell may thereafter be replaced with a redundancy cell. In an example, the ESD may be generated during the packing process at a position where the polyimide layer may open.
FIG. 3 illustrates a fuse opening 25 exposing a fuse part and a section of a semiconductor device having an ESD protection device and an accumulation of ESD generated at the region where the fuse part is opened.
Referring to FIG. 3, the N-type impurity region 12 may be positioned in a P-type semiconductor substrate 10 to form an ESD protection circuit or ESD protection junction diode. A first metal interconnection line 40 and a second metal interconnection line 50 may be connected to the N-type impurity region 12 through conductive plugs 34 and 36, respectively. Accordingly, static electricity generated in the first and second metal interconnection lines 40 and 50 may be discharged through the ESD protection junction diode in order to protect the semiconductor device.
Referring to FIG. 3, the static electricity charge that may be generated during a number of processes (e.g., an opening process of a polyimide layer 80 of a fuse region, a packing process, etc.) may accumulate on a fuse protecting layer 65 on a fuse 20 as well as on the polyimide layer 80 and a passivation layer 70. The ESD protection junction diode may not be able to protect the semiconductor device 100 from the collective ESD accumulated on the polyimide layer 80, the passivation layer 70 and the fuse 20. Since the charge of the polyimide layer 80 may be isolated from the second metal interconnection line 50 by the passivation layer 70, the charge may not flow through the ESD protection junction diode connected with the second metal interconnection line 50. Further, since the charges on the fuse 20 and the passivation layer 70 may not have discharge paths, the charges on the fuse 20 and the passivation layer 70 may likewise not flow through the ESD protection junction diode.
FIG. 4A is a plane photograph illustrating a fuse part of a region where the polyimide layer is opened when the fuse part is receiving an ESD. Referring to FIG. 4A, a reference numeral “1” may indicate that a passivation layer may be pierced by the ESD and a reference numeral “2” may indicate that the fuse part may be damaged by the ESD flowing through the gap (e.g., reference numeral “1”) of the passivation layer.
FIG. 4B is a sectional photograph illustrating an inclined portion of a metal interconnection line damaged due to an ESD generated in positions corresponding to open portions of the polyimide layer. Referring to FIG. 4B, a reference numeral “3” may indicate a plurality of melted portions (e.g., melted by an ESD) of the passivation layer on the metal interconnection line. Although FIGS. 4A and 4B illustrate damaged portions of the fuse and the metal interconnection line, other parts (e.g., a lower structure of the semiconductor device, such as a gate insulating layer) may also be damaged due to the ESD. For example, ESDs may occur frequently at an edge of the opened region of the polyimide layer (e.g., a portion to which an electric field may be strongly applied due to a thin insulating layer or passivation layer).
FIG. 5 is a photograph illustrating an opened portion of the polyimide layer on a fuse part. Referring to FIG. 5, the polyimide layer may have an opening with a rectangular shape. An electric charge may accumulate on an edge 4 of the polyimide layer around the rectangular opening such that damage due to an ESD may occur substantially on a thinner portion of the passivation layer.